The present invention relates to hammer mills, and more particularly, to hammer mills adapted for processing feed material that may contain tramp metal which is to be removed prior to the feed material reaching the hammers.
When grain or other products are passed through a size reduction machine, such as a hammer mill, it is a common practice to meter the feed stock through a metering type feeder. The purpose of the feeder is to level the flow of feed stock so the drive motor can run at an optimum speed without power spikes. One type of metering feeder includes a series of rotating pockets. The pockets are staggered radially and rotated to provide a metered, even flow of feedstock. It is also a common practice to install a magnet in series with the feeder.
The purpose of the magnet is to remove tramp metal in the feedstock before it falls into and damages the mill. In some known arrangements, a stationary magnet is installed in the feeder housing. One disadvantage of this arrangement is that the mill must be stopped, the feeder housing opened, and the tramp metal manually removed from the magnet.
Other known arrangements include pocket feeders with magnets mounted above or below the feeder in a separate housing. In one such arrangement, the magnet is self-cleaning by means of an air cylinder that is activated when the hammer mill motor is turned off. When the air cylinder is thus activated, the tramp metal on a stainless steel plate is pushed away from the face of a magnet and allowed to drop on a pan. One of the disadvantages of having a separate magnet and pocket feeder is that it adds to the height of the hammer mill. Overall height of the machinery is important in the design of the feed mill.